This invention relates to methods and devices for endoscopic vascular surgery, in particular to methods and devices for dissecting tissue to create a working space adjacent a blood vessel.
Numerous surgical procedures have been developed to replace arteries that have become blocked by disease. The aortocoronary bypass surgery is perhaps the most important of these bypass operations. The coronary arteries supply blood to the heart. As a result of aging and disease, coronary arteries may become blocked by plaque deposits, stenosis, or cholesterol. In some instances, these blockages can be treated with atherectomy, angioplasty or stent placement, and coronary bypass surgery is not required. Coronary bypass surgery is required when these other methods of treatment cannot be used or have failed to clear the blocked artery. In coronary bypass surgery, a vein is harvested from elsewhere in the body and grafted into place between the aorta and the coronary artery below the point of blockage. An illustration of this surgery is shown in FIG. 1, which shows the heart 1 and the right anterior coronary artery 2 and the left anterior coronary artery 3 which supply blood to the heart. The right anterior coronary artery 2 is blocked in its proximal segment at 2a, as shown. This blockage has been bypassed by grafting a segment of vein 4 between the aorta 5 and the distal segment 2b of the right anterior coronary artery 2. Similarly, the left anterior coronary artery 3 may be blocked, and may require bypass with a length of vein 4a between the aorta and the distal segment 3b of the left anterior artery. The operation requires access to the heart, which means that the chest cavity must be opened completely.
The coronary bypass surgery requires a length of vein or artery for the graft. It is preferred to use a vein taken from the patient undergoing the bypass surgery. The patient is a ready source of suitable veins that will not be rejected by the body after transplantation and grafting onto the aorta and coronary artery. The saphenous vein in the leg is the best substitute for small arteries such as the coronary arteries, and it is the preferred vein for use in coronary bypass surgery. This is because the saphenous vein is typically 3 to 5 mm in diameter, about the same size as the coronary arteries. Also, the venous system of the legs is sufficiently redundant so that after removal of the saphenous vein, other veins that remain in the leg are adequate to provide return blood flow. The cephalic vein in the arm is an alternative that is sometimes used.
A typical operation previously required to harvest the saphenous vein is illustrated in FIG. 2. The surgeon cuts into the leg to allow access to the saphenous vein and cuts the vein from the leg. To expose the saphenous vein 6, the surgeon makes a series of incisions from the groin 7 to the knee 8 or the ankle 9, leaving a one or more skin bridges 10 along the line of the incisions. Some surgeons make one continuous incision from the groin to the knee or ankle. Handling of the vein must be kept to a minimum, but the vein must be dissected free from connective tissue. After exposing the vein, the surgeon grasps it with his fingers while stripping off the surrounding tissues with dissecting scissors or other scraping instruments. The surgeon uses his fingers and blunt dissection tools to pull and lift (or mobilize) the vein from the surrounding tissue. The vein is mobilized or pulled as far as possible through each incision. To reach under the skin bridges, the surgeon lifts the skin with retractors and digs the vein free. While stripping the vein, the surgeon will encounter the various tributary veins that feed into the saphenous vein. These tributaries must be ligated and divided. To divide and ligate tributaries that lie under the skin bridges, the surgeon may need to cut one end of the saphenous vein and pull it under the skin bridge to gently pull the vein out from under the skin bridge until the tributary is sufficiently exposed so that it may be ligated and divided. When the vein has been completely mobilized, the surgeon cuts the proximal and distal ends of the vein and removes the vein from the leg. After removal, the vein is prepared for implantation into the graft site, and the long incisions made in the leg are stitched closed.
The procedure described above can be used to harvest veins for a femoral popliteal bypass, in which an occluded femoral artery is bypassed from above the occlusion to the popliteal artery near the level of the knee. The procedure can also be used to harvest veins for the revascularization of the superior mesenteric artery which supplies blood to the abdominal cavity and intestines. In this case, the harvested vein is inserted between the aorta to the distal and patent (unblocked) section of the mesenteric artery. For bypass grafts of the lower popliteal branches in the calf, the procedure can be used to harvest the umbilical vein. The harvested vein can also be used for a vein loop in the arm (for dialysis) between the cephalic vein and brachial artery.
As can be seen from the description above, the vein harvesting operation is very traumatic in its own right. In the case of coronary artery bypass, this operation is carried out immediately before the open chest operation required to graft the harvested vein into the coronary arteries. The vein harvesting operation is often the most troublesome part of the operation. The long incisions created in the leg can be slow to heal and very painful. Complications resulting from the vein harvesting operation can also hinder the patient""s recovery from the entire operation.
The method of vein harvesting presented herein is accomplished with laparoscopic procedures. This allows the veins to be harvested in an operation that requires only a few small incisions. Endoscopic surgical techniques for operations such as gall bladder removal and hernia repair are now common. The surgeon performing the operation makes a few small incisions and inserts long tools, including forceps, scissors, and staplers, into the incision and deep into the body. Viewing the tools through a laparoscope or a video display from the laparoscope, the surgeon can perform a wide variety or maneuvers, including cutting and suturing operations, necessary for a wide variety of surgical procedures and operations.
Minimally invasive procedures for vein removal have been proposed. U.S. Pat. No. 5,373,840 to Knighton, entitled, xe2x80x9cEndoscope and Method for Vein Removal,xe2x80x9d shows a method of cutting the saphenous vein at one end, and grasping the vein with graspers or forceps, then sliding a ring over the vein while holding it. Knighton uses a dissecting tool with an annular cutting ring, and requires that the saphenous vein be overrun or progressively surrounded with the dissecting tool and the endoscope, so that after the endoscope has been inserted as far as it will go, the entire dissected portion of the vein has been pulled into the lumen of the endoscope. As shown in FIGS. 1 and 10 of Knighton, the method requires deployment of forceps inside the annular dissection loop, and it requires deployment of the loop and graspers inside the endoscope lumen. The blood vessel must be cut and grasped by the forceps before it can be dissected by the dissecting ring.
The methods and devices disclosed herein allow surgeons to harvest veins, or dissect along other elongate structures without making long incisions through the skin to access the structure as previously required. The present devices permit minimally invasive procedures which, in the case of a saphenous vein harvest, require just two small incisions, one at either end of the saphenous vein, to be performed. The procedure is accomplished with laparoscopic instruments under the guidance of a laparoscope.
In a first preferred embodiment, a blunt loaded balloon dissector has an elongate balloon of any suitable length which may be formed of an elastic or non-elastic material. The balloon may be of double walled construction and may be provided with a central lumen which may receive a guide rod, scope or other surgical instrument. The device may have a support tube secured to the inner wall of the balloon to provide columnar support for the apparatus.
The guide rod and/or support tube are normally straight and must have sufficient rigidity to bluntly dissect while tunneling between connected tissue layers. In a further aspect of the present invention, the guide rod and/or support tube, while being rigid enough to bluntly dissect, are also plastically bendable into curved shapes when subjected to bending moments substantially greater than the bending moments encountered when dissecting between tissue layers. The guide rod and/or support tube permanently retain the curved shape under the forces and conditions of blunt dissection. The support tube receives the guide rod, scope or other surgical instrument and may have a stop member to translate pushing force applied to the guide rod or scope to pushing force on the apparatus. By using the guide rod or scope as a pushing member the apparatus may be advanced alongside the vessel it is desired to dissect free from attached tissue. A balloon cover which may be elastic or resilient is provided to surround the balloon and facilitate compression of the balloon after it is deflated.
In another embodiment of the invention, another pushable balloon dissection device is provided which also may utilize an elongate balloon. The balloon in this embodiment may have a central lumen to receive a scope or other laparoscopic instrument. The apparatus has a guide tube which receives a guide rod with a slender metal rod and enlarged tip. The guide rod is utilized as a pushing member. A resilient balloon cover may also be provided in this embodiment to compress the balloon upon deflation.
In yet another preferred embodiment of the invention, a pushable balloon dissection apparatus may have an elongate balloon disposed over an elongate shaft or tubular member such that the shaft or tubular member resides within the interior space of the balloon. The balloon dissector may be advanced between the tissue planes it is desired to dissect and then inflated to create a tunnel alongside a vessel or other elongate structure. The balloon may then be serially deflated, further advanced and reinflated to enlarge the tunnel. When the apparatus is provided with a tubular member, a laparoscope may be inserted into the bore of the tubular member and utilized as a pushing member to advance the apparatus and to provide observation of the procedure. A resilient balloon cover may also be utilized in this embodiment to assist in deflating and compressing the balloon to facilitate redeployment of the apparatus.
In another aspect of the invention, a preferably transparent, or translucent, shroud may be attached to the distal end of the tubular member. The shroud extends beyond the distal end of the tubular member. A distal section of the shroud covers the opening of the tubular member such that there is an open space between the distal end of the tubular member and the distal section of the shroud. The shroud may have a generally spoon-shaped form. The shroud can be used to perform blunt dissection and/or retraction to create an open space for viewing or for performing surgical procedures. A resilient balloon cover may also be used with the tubular member having a shroud to compress the balloon upon deflation.
In still another aspect of the present invention, the dissector may have an ergonomic handle at its proximal end. The handle is designed to fit comfortably in one hand of a surgeon and to provide the surgeon greater control of the dissector during insertion and placement. The ergonomic handle may be adapted to receive and to provide supplementary support for a scope instrument, and can also hold a light source for the scope instrument.
The method of vein harvesting disclosed herein utilizes an elongate tubular balloon to dissect a tunnel alongside the vein to be harvested. The elongate balloon may be wrapped around a guide rod or endoscope and inserted through a small incision in the leg and pushed along the vein to create a small tunnel over the vein. The elongate balloon may be provided with a balloon cover which may be a separate removable cover or attached to the balloon. When the balloon is in place adjacent the vein to be dissected, the removable balloon cover (if provided) may be removed and the balloon inflated to enlarge the tunnel and create a working space for insertion of endoscopic instruments. The guide rod or endoscope may be removed to allow other endoscopic instruments to be passed into the tunnel through the balloon.
In a preferred method of harvesting the saphenous vein, the surgeon makes one small incision at each end of the saphenous vein. After making the incisions, the surgeon inserts a tunneling instrument or blunt dissector which carries a long balloon into one incision and advances or pushes the dissector along the saphenous vein to make a small tunnel along the saphenous vein. The surgeon then inflates the long balloon to enlarge the tunnel. When the tunnel is enlarged to an appropriate size, the surgeon removes the balloon and seals the tunnel at both ends. The surgeon may then injects carbon dioxide into the tunnel at sufficient pressure (typically 5-15 mm Hg) to inflate the tunnel and create room for laparoscopic instruments. The surgeon then inserts a laparoscope through the seal to provide a view of the procedure, and inserts a laparoscopic vein harvesting device, such as one of the hooked vein harvesting devices disclosed in copending U.S. application Ser. No. 08/444,424 entitled, xe2x80x9cMethods and Devices for Blood Vessel Harvesting,xe2x80x9d into the leg to dissect the connective tissue from the vein, identify side branches, and remove the vein from the leg. The disclosure of the aforementioned application Ser. No. 08/444,424 is hereby incorporated by reference in its entirety. After the vein is loosened or dissected free from its channel in the leg, the surgeon can cut the proximal and distal ends of the vein and easily pull the vein from the leg. The small skin incisions are then stitched so that they may heal. The small incisions heal much more readily, with fewer complications and far less pain, than the open procedures now in use.